7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase (HPPK) has been expressed from E. coli. It is the first enzyme in folate synthesis. Unlike mammalian cells that take up folate cofactors from the diet, most microorganisms must synthesize folates de novo, since they lack the transport pathway. For this reason, HPPK is important as a potential target for selective antimicrobial chemotherapy. Data for native protein have been collected at 1.6 E resolution (space group P21, a=36.3 E, b=51.9 E, c=41.2 E, =110.3 , Rsym=4.4%). Other data collected: HPPK / MgATP complex: single wavelength data at 1.6 A. HPPK / HP complex: single wavelength data at 2.1 A.